Mortuary + Altar of Dementia + Bolas's Citadel + Tarpan

Mortuary

Altar of Dementia

Bolas's Citadel

Tarpan

How it works

1. Activate Altar of Dementia by sacrificing Tarpan.
2. When Tarpan dies, it and Mortuary triggers.
3. Resolve the Mortuary trigger, putting Tarpan from your graveyard onto the top of your library.
4. Resolve the Tarpan trigger, causing you to gain 1 life
5. Resolve the Altar of Dementia ability.
6. Cast Tarpan from the top of your library by paying 1 life due to Bolas's Citadel.
7. Repeat.

This loop creates an engine for infinite mill and lifegain by leveraging Mortuary's continuous replacement effect to immediately recycle sacrificed creatures back to your library. Altar of Dementia acts as the sacrifice outlet that bins the creature and mills your opponent, while Tarpan provides the crucial life buffer needed to sustain the process. Finally, Bolas's Citadel ties the whole strategy together by turning the top of your library into your hand, letting you recast the looping Tarpan by paying life instead of mana.